(not applicable)
Compression Ignited Direct Injection (CIDI) engines, as diesel engines, emit more pollution than necessary because conventional fuel injection systems as presently employed cannot control fuel delivery with sufficient accuracy during cold starts and load/speed transients.
At the present, fuel injection systems purport to control the overall injection rate by controllably raising and lowering mean injection pressure (MIP). When the injection orifice size is fixed in the fuel injector, there is unavoidably poor atomization at low injection rates, and while at the usual relatively low engine cranking speed, there is both poor atomization of the fuel as well as an excessive injection rate. With currently employed injectors, therefore, there is little flexibility in shaping the injection rate/crank angle curve during engine operation to maximize or increase fuel injection and engine efficiency. Typical prior art injection nozzles are shown in List U.S. Pat. No. 4,892,065, Kopse U.S. Pat. No. 4,339,080, and Klomp U.S. Pat. No. 4,096,995, for example, among others.
In the preferred variable orifice fuel injector (VOECRRI) of the invention, the injection rate of the diesel fuel is specifically controlled by varying the effective size of the orifice or orifices through which fuel flows into the engine. Further, in accordance with the invention, the VOECRRI can be designed to fit within a 14 or 15 mm. cylinder or even a smaller cylinder, which advantageously allows it to be used with relatively tiny four-valve cylinders in four cylinder 1.2 liter CIDI engines, for example. Such small engines are particularly desired and required as diesel engines for use in hybrid electric vehicles, and wherein space for fuel injection equipment is very limited.
Additionally, the VOECRRI of the invention contributes to reduction in pollution from diesel engines, is less costly to manufacture than currently employed common rail systems, thereby enhancing widespread use and standardization on diesel engines. Further, diesels operate more satisfactorily with a slower start of fuel injection, which is readily accomplished with the injector structure of the invention.
The VOECRRI herein is a variable orifice, multi-orifice injector as a key component of an electronically controlled high-pressure common rail fuel injection system. While an electronically controlled actuator is preferred, the invention may also be employed with a hydraulic actuator.
A feature of the invention lies in the provision of a hollow or tubular fuel feed needle sliding within a ported cylindrical barrel adjacent the usual closed sac at the tip of the assembly, whereby fuel injection flow may be controlled by the axial position of the needle with respect to the injection orifices.